Fun Nipping Or Fin Rot? Treatment

[CLC9179]

We have a fairly new tank with 8 glofish and 1 black skirt tetra.

We did fishless cycling using ammonia before getting the fish. The tank is cycled with ammonia at 0 and nitrite at 0. Nitrates have never been over 10 since we added fish, and we are changing about 30% of the water each week.

We've had the fish for about 3 weeks now and added the last fish almost exactly 10 days ago.

The black skirt tetra has some pieces missing from his back/tail fin. I can't tell if it's from nipping or fin rot. None of the other fish seem to have pieces missing though.

Is it possible to get fin rot with good water parameters and have only one fish affected?
Or is it more likely someone nipping? We have two long fin glofish, and they are fine, but the black skirt definitely has the longest fins. How would you treat the fish?

Could stress of being the only black skirt tetra be contributing to fin rot? Should we get more black skirt tetras? We have a 20 gallon tank and don't think we can add enough to get to 5 black skirts. The fish generally seem to be getting along ok, but I want/need to add some live plants too.

 

[Sage Exotics]

With glofish, I’d say it’s most probably fin nipping, you could add some medication like betta-fix but that’s only if it’s serious, in a 20 gallon I’d definitely add at least two more skirt tetras to help out the current tetra. the plants are an awesome idea, they don’t dirty up the tank like fish, in fact, they act like filters (although you still need a filter of course).

 

[CLC9179]

Oh and just to clarify, they are
Glofish tetras, not the danios.

With glofish, I’d say it’s most probably fin nipping, you could add some medication like betta-fix but that’s only if it’s serious, in a 20 gallon I’d definitely add at least two more skirt tetras to help out the current tetra. the plants are an awesome idea, they don’t dirty up the tank like fish, in fact, they act like filters (although you still need a filter of course).

AlL of the glofish are tetra, not sure if that changes things. Would you still add 2 more black skirts?

 

[Sage Exotics]

It changes nothing, tetras are notorious fin nippers, I’d add some more skirts still.

 

[CLC9179]

It changes nothing, tetras are notorious fin nippers, I’d add some more skirts still.

Thanks!!